The primary objectives of the project are to determine: 1) whether Z toxin, detected in tissue culture, is identical to or different from Liu's lethal toxin as well as other exotoxins previously described as being elaborated by Pseudomonas aeruginosa: 2) whether different strains of P. aeruginosa produce a single or multiple type-specific toxin (s) which produce cytopathogenicity in cell culture monolayers; and 3) whether such toxin is directly related to bacterial plaque formation in cell culture monolayers. The long range objective of this project is to apply in vitro models which incorporate host cells in tissue culture to study the pathogensis of P. aeruginosa infection.